Also then I choose at "Performance Mode" in the Advance and Overclocking section on my ASUS mobo, I can turn it to "TURBO" but id I do this the whole computer doesn't start up...

Please tell me How far I can push the CPU External Frequency (MHz)??? It goes to 400MHZ , what will happen if i do this? And did i do well in putting the DRAM frequency to 400 MHz , the actual frequency of my DDR ram???

Please enlighten me a bit more on this overclocking business.. Also I need to know if 70 Celcius is puhing the Prescott 2.8 Ghz too much ,,, any safe running temps ???And when the CPU is so-called Throttling , is that a bad thing right, we don't want that???

Ouch buddy! Did you try any lesser overclocks first, say 205, then maybe 210, and so forth. Just jumping to 240 is a bit premature to say the least... And as far as I am concerned 70C is too hot for any cpu to run. Are those temps. stock or overclocked?

I even more confused , I overclocked a prescott 2.8 at 240 Frequency, and the Temp read like this : Motherboard = 35CelsiusCPU = 49.5Celsius

Is this a problem then... My first question included "To how far can I push the FSB Frequency???

on the ASUS P4P800SE board there is is also the option for automatic overclocking up to 20 % or 30% (i can remember) , Putting it on this setting pusses the CPU Frequency to 3.36 for a 2.8 GHz cpu , is this ok to do???

I think what we are suggesting, is that you OC in small increments. Testing for stability often. You may need to do more to reach those speeds, i.e. higher voltage, aftermarket cooling. If you read the article then why are you asking us why your system won't boot after randomly jumping the FSB all the way from 200 to 240. That's a big change dude. Typically not reccomended. Try lowereing the FSB mhz by mhz until the system boots and is stable. Then we'll work from there.......

There aren't any jumpers to worry about. Do not use the auto-overclock/turbo/corecell mode. Overclcok in BIOS and stay there. You should be able to hit 3.4 ghz at or close to stock voltage. HOWEVER, 70C is too hot. You need a ducted 3G case and plenty of fans. Punch your Vdimm up to 2.7 or 2.8v and maybe +.05v if you need it. You should really start from 200mhz and move up in 6mhz increments noting the stability and temperature along the way. If you run Aquamark3 you will heat that puppy up and notice the improvements in speed along the way.